Sensor device and flicker noise mitigating method

1. A sensor device, comprising:

a fingerprint sensing module, configured to sense a first raw image using a first exposure time; and

an exposure time adjusting module, configured to perform the following steps:

obtaining a first image according to the first raw image;

determining whether the first image comprises a flicker noise; and

adjusting the first exposure time when the first image comprises the flicker noise to mitigate the flicker noise;

wherein the flicker noise causes light strips and dark strips alternatively appearing in the first image.

2. The sensor device of claim 1 , wherein in the obtaining the first image, wherein the exposure time adjusting module is further configured to perform a fixed pattern noise reduction operation on the first raw image to generate the first image.

3. The sensor device of claim 1 , wherein the first image comprises a plurality of pixel rows each comprising a plurality of row pixels, and the exposure time adjusting module is further configured to perform the following steps, to determine whether the first image comprises the flicker noise:

aggregating the plurality of row pixels within the each row pixel array to obtain a representative pixel column, wherein the representative pixel column comprises a plurality of representative column pixels;

obtaining a variance of the plurality of representative column pixels; and

determining whether the first image comprises the flicker noise according to the variance.

4. The sensor device of claim 3 , wherein the exposure time adjusting module is further configured to perform the following step, to determine whether the first image comprises the flicker noise according to the variance:

determining that the first image comprises the flicker noise when the variance is greater than a threshold value.

5. The sensor device of claim 1 , wherein the exposure time adjusting module is further configured to perform the following steps, to determine whether the first image comprises the flicker noise:

determining whether the first image comprises a light strip;

determining whether the first image comprises a dark strip; and

determining whether the first image comprises the flicker noise according to a total number of the light strip and the dark strip.

6. The sensor device of claim 5 , wherein the determination that the first image comprises the flicker noise according to a total number of the light strip and the dark strip comprises:

determining that the first image comprises the flicker noise when the total number of the light strip and the dark strip is greater than a threshold of total strips.

7. The sensor device of claim 5 , wherein the determination of whether the first image comprises a light strip comprises:

determining whether the light strip comprises a plurality of light pixel rows sequentially arranged in a column direction, wherein pixel values corresponding to pixels within the light strip are greater than a light brightness threshold; and

determining whether a total row number of each pixel row within the light strip is greater than a strip width threshold.

8. The sensor device of claim 5 , wherein the determination of whether the first image comprises a light strip comprises:

determining whether the light strip comprises a plurality of dark pixel rows sequentially arranged in a column direction, wherein pixel values corresponding to pixels within the dark strip are less than a dark brightness threshold; and

determining whether a total row number of each pixel row within the dark strip is greater than a strip width threshold.

9. The sensor device of claim 1 , wherein the fingerprint sensing keeps module sensing images using the first exposure time when the exposure time adjusting module determines that the first image comprises no flicker noise.

10. The sensor device of claim 1 , wherein the fingerprint sensing module is further configured to sense a second raw image using a second exposure time, the second exposure time is an adjusted exposure time which is adjusted based on the first exposure time, and the exposure time adjusting module is further configured to perform the following steps:

receiving a second image, wherein the second image is related to the second raw image; and

determining whether the second image comprises a flicker noise;

wherein the fingerprint sensing module keeps sensing images using the second exposure time when the exposure time adjusting module determines that the second image comprises no flicker noise.

11. The sensor device of claim 10 , wherein the exposure time adjusting module is further configured to perform the following step:

performing a fixed pattern noise cancelling operation on the second raw image, to generate the second image.

12. The sensor device of claim 1 , wherein the exposure time is a time interval between a reset time and a readout time of a light sensing element within the fingerprint sensing module.

13. The sensor device of claim 12 , wherein the light sensing element is a photo diode.

14. The sensor device of claim 1 , wherein the sensor device is disposed under a display panel of an electronic device.

15. An image processing device for a sensor device, wherein the sensor device comprises an image fingerprint sensing module configured to sense a first raw image of a fingerprint using a first exposure time, the image processing device comprises:

an exposure time adjusting module, configured to perform the following steps:

obtaining a first image according to the first raw image;

determining whether the first image comprises a flicker noise; and

adjusting the first exposure time when the first image comprises the flicker noise to mitigate the flicker noise;

wherein the flicker noise causes light strips and dark strips alternatively appearing in the first image.

16. The image processing device of claim 15 , wherein the first image comprises a plurality of pixel rows each comprising a plurality of row pixels, and the exposure time adjusting module is further configured to perform the following steps, to determine whether the first image comprises the flicker noise:

aggregating the plurality of row pixels within the each row pixel array to obtain a representative pixel column, wherein the representative pixel column comprises a plurality of representative column pixels;

obtaining a variance of the plurality of representative column pixels; and

determining whether the first image comprises the flicker noise according to the variance.

17. The image processing device of claim 15 , wherein the exposure time adjusting module is further configured to perform the following steps, to determine whether the first image comprises the flicker noise:

determining whether the first image comprises a light strip;

determining whether the first image comprises a dark strip; and

determining whether the first image comprises the flicker noise according to a total number of the light strip and the dark strip.

18. A flicker noise mitigating method, applied in a sensor device, the flicker noise mitigating method comprising:

sensing a first raw image using a first exposure time;

obtaining a first image according to the first raw image;

determining whether the first image comprises a flicker noise; and

adjusting the first exposure time when the first image comprises the flicker noise to mitigate the flicker noise;

wherein the flicker noise causes light strips and dark strips alternatively appearing in the first image.

19. The flicker noise mitigating method of claim 18 , wherein the first image comprises a plurality of pixel rows each comprising a plurality of row pixels, and the step of determining whether the first image comprises the flicker noise comprises:

aggregating the plurality of row pixels within the each row pixel array and to obtain a representative pixel column, wherein the representative pixel column comprises a plurality of representative column pixels;

obtaining a variance of the plurality of representative column pixels; and

determining whether the first image comprises the flicker noise according to the variance.

20. The sensor of claim 18 , wherein the step of determining whether the first image comprises the flicker noise comprises:

determining whether the first image comprises a light strip;

determining whether the first image comprises a dark strip; and

determining whether the first image comprises the flicker noise according to a total number of the light strip and the dark strip.

21. A flicker noise mitigating method, applied in an electronic device comprising a display panel and a sensor device, the flicker noise mitigating method comprising:

generating one or more first signals for controlling a plurality of light emitting elements of the display panel to emit light according to a frame rate;

generating one or more second signals for controlling a plurality of light sensing elements of the sensor device to sense light so as to generate an image according to an exposure time;

setting an initial value of the exposure time according to the frame rate; and

adjusting the exposure time to mitigate flicker noise of the image;

wherein the flicker noise causes light strips and dark strips alternatively appearing in the image.